@@ -124,7 +124,7 @@ class Chatgpt(SimpleService):
                 raise FileUploadUnsupported
             file_service = FileProcessingService
             file_bytes = input_message.file.read()
-            kind = filetype.guess(file_bytes[:20])
+            kind = filetype.guess(file_bytes[:550])
             if not kind:
                 raise CorruptedFileError
             raw_file_extension = kind.extension
@@ -109,7 +109,7 @@ class Chatgpt_5(Chatgpt):
         if file:
             file_service = FileProcessingService
             file_bytes = input_message.file.read()
-            kind = filetype.guess(file_bytes[:20])
+            kind = filetype.guess(file_bytes[:550])
             if not kind:
                 raise CorruptedFileError
             raw_file_extension = kind.extension
@@ -124,7 +124,7 @@ class Chatgpt_5_4(Chatgpt):
         if file:
             file_service = FileProcessingService
             file_bytes = input_message.file.read()
-            kind = filetype.guess(file_bytes[:20])
+            kind = filetype.guess(file_bytes[:550])
             if not kind:
                 raise CorruptedFileError
             raw_file_extension = kind.extension
@@ -79,7 +79,7 @@ class Claude(SimpleService):
             file_service = FileProcessingService
             try:
                 file_bytes = input_message.file.read()
-                kind = filetype.guess(file_bytes[:20])
+                kind = filetype.guess(file_bytes[:550])
                 raw_file_extension = kind.extension
                 file_extension = file_service.get_file_extension(raw_file_extension, file_bytes)
                 if file_extension in ('pdf', 'doc', 'docx', 'xlsx'):
@@ -136,7 +136,7 @@ class Gemini(SimpleService):
         if file:
             file_service = FileProcessingService
             file_bytes = input_message.file.read()
-            kind = filetype.guess(file_bytes[:20])
+            kind = filetype.guess(file_bytes[:550])
             raw_file_extension = kind.extension
             file_extension = file_service.get_file_extension(raw_file_extension, file_bytes)
             if file_extension in ('pdf', 'doc', 'docx', 'xlsx'):
@@ -86,7 +86,7 @@ class Gemini_3_1(SimpleService):
         if input_message.file:
             file_service = FileProcessingService
             file_bytes = input_message.file.read()
-            kind = filetype.guess(file_bytes[:20])
+            kind = filetype.guess(file_bytes[:550])
             raw_file_extension = kind.extension
             file_extension = file_service.get_file_extension(raw_file_extension, file_bytes)
             if file_extension in ('pdf', 'doc', 'docx', 'xlsx'):
@@ -57,7 +57,7 @@ class Grok_4_1_Fast(SimpleService):
         if input_message.file:
             file_service = FileProcessingService
             file_bytes = input_message.file.read()
-            kind = filetype.guess(file_bytes[:20])
+            kind = filetype.guess(file_bytes[:550])
             if not kind:
                 raise CorruptedFileError
             raw_file_extension = kind.extension
@@ -74,7 +74,7 @@ class Qwen_3_5(SimpleService):
         if input_message.file:
             file_service = FileProcessingService
             file_bytes = input_message.file.read()
-            kind = filetype.guess(file_bytes[:20])
+            kind = filetype.guess(file_bytes[:550])
             raw_file_extension = kind.extension
             file_extension = file_service.get_file_extension(raw_file_extension, file_bytes)
             if file_extension in ('pdf', 'doc', 'docx', 'xlsx'):
@@ -80,7 +80,7 @@ class Raifgpt(Chatgpt):
         if file:
             file_service = FileProcessingService
             file_bytes = file.read()
-            kind = filetype.guess(file_bytes[:20])
+            kind = filetype.guess(file_bytes[:550])
             if not kind:
                 raise CorruptedFileError
             raw_file_extension = kind.extension